Packaging apparatus and method



June 30, 1959 H. w. LA BRANCHE 9 PACKAGING APPARATUS AND METHOD Filed March 1, 1957 v a Sheets-Sheet 1 /20 H0 L ugmvronh v GI'VEy G I'CIIIC e F1921. BY a f Jime 30, 1959 H. w. LA BRANCHE PACKAGING APPARATUS AND METHOD Filed March 1, 1957 Sheets-Sheet 2 INVENTOR.

Harvey LaBran che HHy.

June 30, 1959 w, BRANCHE 2,892,294

PACKAGING APPARATUS AND METHOD Filed March 1, 1957 3 Sheets-Sheet '3 ill" INV EN TOR. Harvgy LaBz'an 6116 United States Patent PACKAGING APPARATUS AND METHOD Harvey W. La Branche, Tacoma, Wash., assignor to Washington Steel Products, Inc., Tacoma, Wash., a corporation of Washington Application March 1, 1957, Serial No. 643,355 13 Claims. (Cl. 53-112) This invention relates to apparatus and method for packaging articles in a thermoplastic sheet preliminary to storing, shipping and selling them.

For efiicient plant operation the apparatus and method employed for packaging articles in a thermoplastic sheet should meet several important requirements. For example, the apparatus should be adaptable for use with both drape-forming and vacuum-forming techniques. It should be applicable interchangeably to the packaging of large articles and small articles.

Still further, the apparatus should be adjustable to accommodate plastic sheets of varying thickness and physical properties. It should be possible to package the articles on a backing sheet, when desired, in order to lend rigidity and strength to the final package. The apparatus should be operable manually or automatically at the will of the operator in order to operate the apparatus initially on an experimental scale to work out suitable conditions for packaging particular articles with plastic sheets of given properties, and thereafter to set the apparatus for packaging the articles automatically under the predetermined optimum conditions.

It also is desirable to provide apparatus wherein the articles being packaged are clearly visible to the operator and wherein the operator is protected from injury. Furthermore, the rate of plastic pull-down during the forming operation should be controllable so that it will not pull the articles out of position as it is molded about them, nor will it be unduly stretched during the molding operation. Also, it is highly desirable that the vacuum applied be variable to accommodate fragilearticles which would not stand full atmospheric pressure during the packaging procedure.

It is the general object of the present invention to provide packaging apparatus and method which meets all of the foregoing requirements but which nevertheless is of simple, inexpensive, construction so that it may be purchased, used, and serviced at low cost.

The manner in which the foregoing and other objects of this invention are accomplished will be apparent from the accompanying specification and claims considered together with the drawings, wherein:

Fig. 1 is a diagrammatic view of the herein described packaging apparatus including a diagram of the electric circuit by which it is operated;

Fig. 2 is a view in front elevation of the herein described packaging apparatus;

Fig. 3 is a view in side elevation of the herein described packaging apparatus;

Fig. 4 is a detail view, partly in section, depicting in side elevation the means employed for positioning the articles and plastic sheet relative to each other for packing the articles with the sheet;

Fig. 5 is a detail view in side elevation of an adjustable clamp employed for holding the plastic sheet in the holding means of Fig. 4;

Fig. 6 is a detailview, partly in section, of meansemployed for adjusting the clamping assembly to receive plastic sheets of varying thickness; and

Fig. 7 is a fragmentary enlarged sectional view illustrating the manner of applying the presently described packaging apparatus and method to the packaging of articles on an adhesive covered, porous, backing sheet.

Generally stated, the herein described packaging apparatus comprises a perforated support for the articles, clamping means for clamping a thermoplastic sheet across the articles, heating means positioned on the side remote from the articles for softening the sheet, means for moving the softened sheet and the articles relative to each other for draping the sheet about the articles, differential air pressure means communicating with the perforations on the support for applying differential air pressure, pref-- erably vacuum, to the softened draped sheet, thereby forming it about the articles and means for cooling the soft, formed sheet about the articles to form the final rigid package.

Application of the foregoing apparatus makes possible the efiectuation of a novel packaging method which comprises placing a thermoplastic sheet across the articles to be packaged, softening the sheet, draping the softened sheet about the articles, and then applying differential air pressure to form the softened, draped sheet about the articles to form the final package. It also makes possible eitectuation of a method applicable where a rigid package is required and comprising the steps of placing the articles to be packaged on a porous backing sheet such as a sheet of cardboard or other fibrous material having thereover a perforated layer of thermosensitive adhesive, superimposing a thermoplastic sheet above the articles and the backing sheet, heat softening the thermoplastic sheet, and molding the plastic sheet about the articles while pressing it against the adhesive on the backing sheet, thereby encasing the articles and adherently uniting the packaging sheet to the backing sheet.

Considering the foregoing in greater detail and with particular reference to the drawings:

The forming chamber The herein described packaging apparatus and method may be applied to the covering or packaging of a wide variety of items. It may be applied, for example, to the packaging of such items as knives, can openers, bottle caps, hinges, drawer pulls, door knobs, clusters of screws and nails, etc. In the presently described embodiment it is illustrated in connection with the packaging of a plurality of screws 10 arranged in clusters.

The articles are packaged in apparatus mounted in a housing 12 which is built around and rigidified by a compartmented vacuum tank 14. An instrument panel 16 is located at the front of the apparatus. A roll of the thermoplastic sheet material 18 is rotatably mounted in brackets 20 on one side of the apparatus, guides 22, 24 being placed on opposite sides of the apparatus for guiding the plastic sheet. The apparatus thus is made operable from either direction by mounting brackets 20 on one side or the other, as required by the direction of material flow in the plant.

The articles to be packaged are located over a vacuu box 30, the floor of which is provided with discontinuous spacers 31 which support a perforated plate 32. The perforations in this plate are arranged in any desired pattern as required to form the plastic sheet about the articles. Also, the plate may either be flat, as where a general purpose packaging operation is contemplated, or provided with locating projections suitable for use in placing specific articles in proper position on the plate.

Vacuum box 30 communicates with a conduit 33 (Fig;

1). This conduit communicates with vacuum tank 34, which is one of the compartments of tank 14, through a two-way valve 36 operated by solenoid 38.

The sheet cldmpirig unit .Thermoplastic sheet 13 b :clamped across articles 1055 thy ry i bdplate 32byn eans of an assembly, the construction .0; which is particularly apparentfroma consideration of Figs Thusit comprisesa lower rectangular frame member 40 and ,aregistering,upper rectarigula'r frame member. A sealing ring made of rubber or. other suitable material is. provided onthe under surface of lower franie membenfit}. Another s ealin grin'gfltitis provided on the upper surface thereof, Aceor ingly wheintlie claniping frame is placed on the top, Qt hbus ing .1 a, sealed v vacuum molding chamber is formedwhich ,is defined plate 32;; lower clamping frame member 40', and plastic sheet 18.

t ap er canni flniem j b r his. ra e t the lower member by,,an.assembly which pennits adjust merit of the spacebetween thetwo frame members as accommodate plastic sheets of varying thickness. Accordingly, there are provided two orrnore spaced standards 48; bolted onto lower frame, member 40 by means of bolts50, A cross piece 52 having on its underside a pair of spaced recesses 54 is pivotally connected to each rd by ni iw t Piv t P n springs Accordingly sufficient pressure is exerted against the lightest materials to fo'rman air seal between the plastic sheet and sealing ring 46. Heavier material compresses the springs further, developing greater sealing r Ili'etront: s'ide of the clamping frame is provided with n' me ns whi a sq may be, a -t c omnibdato plastic sheets of varying thickness; constructiii of the l'atch employed is" illustrated particularly in Figs. 2, 4" and'S.

Bahamian is mounted on an extension64 of lower frame member 401 It'includesa base 66 upon which are mounted apair ofspac'ed plates 68. I v

A U-shaped lever arm 70..is" pivotally connected to theplates means or pin 72. Lever arm 70 is cjon-' necte'd through pivoting'dinks 74; to a .bar 76'. which is.

pivotally mounted be'tween plat'e's 6 8' by means of pin 78. A bolts!) is threaded into theouter end of bar 76.

Th'erelati'onship of lever armjm, links 74 and bar 76' is" su'ch that when the assembly is shifted from. the

position of Fig. to that of Fig. .4, a tog'gle action occurs which holds the head'of bolt 80 firmlyagainst the upper surface of upper frame member 42, thus clamping it against the lower frame member; In addition, by ad justing bolt 80 the degree of pressure, or the spacing betweenthe two frame members, may be'adjustd to accornrnodate plastic sheets of, varying thickness.

t .The clampingj frame assembly alsoincludes a handle 82 and a mold box segment 84. The latteris rectangular inshape and maybe placed on plate 32 inside frame sections 4 0, 42 when it is desired to provide a. mold hox of substantial depth This may be desirable, for

ekan ple,. vvh6n he plastic s heet is to be drawn into female molds placed on plate 32.

. 4 The vacuum system Means are provided for reciprocating the clamping frame assembly between an elevated position wherein it is spaced apart from plate 32, which supports the articles to be packaged, and a lowered position wherein it is in sealing engagement with the plate and forms a mold box about the articles. To this end, it may be supported on the piston rods ofv vacuum operatedrcylinders 92. These cylinders are connected to a source of vaeuum by av system including conduit 94 which interconnects the cylinders above the pistons thereini and a conduit 96 which interconnects the cylinders below the pistons. Conduit 94 .connectswitha conduit98 which leads to a four-way valve 100 operated by means of a solenoid 102. Conduit 96 connects with a conduit 104 which includes one-Way throttle valve 106 and also connects with four-way valve 100. Valve 100 is connected to a source; of vacuum by means of conduit.10&.which.communicateswithvacuum tank 110'. Thistank in .turn is one of the compartmentsoftank 14 about which the frameof; the apparatusisbuilt. V

Ianlefid, which exhausts vacuum chamber 30, and tank 110, which driyes cylinders 92, areinterconnected through line ll z. This,lineiincludes avalve 11,4 operated by solenoid 11 6 and adjusted by ,switchllli .Tanks 34, 110 thusmay-be eyacuated by a commonvacuum pump driven by motor 122 andcommunicating with tank 110 through conduit 124, which includes check valve 125. I The f oregoingarrangement makes. it possible to apply full yacuum tocylinders 92 while applying only apartial vacuumto. vacuum chamber, 30,.as maybe required bythefragile character of articles 10,.being. packaged which may not be able to withstandfull atmospheric pressure. It also makes possible, by setting valve.114, variation of thevacuum pressureapplied to, chamber 30 to suit the needs of variousclassesof articles. S till further, inclusion of throttle valve 106 .in. the line to cylinders 9 2makes possible retracting the cylinders at a relatively slow rate While advancing them rapidly. This is desirable since ifthe cylinders are retracted too rapidly, articles 10 on'the supporting ,plate may be jarred out .of position, ,Still; further; .the herein described vacuum circuitinsures that ,the clamping frame assembly will have a uniform positive; action over. a prolonged period of operation in spiteofthe fact that variable degreesoi vacuumnraybe applied to vacuum chamber 30. Means also are present for introducing air into vacuum chamber 30 at. the conclusion of a forming cycler The air. thus introduced. may be at atmospheric or elevated pressure, as desired. It is introduced through conduit 126 which. connectsconduit. 33 with a,so urce of air 128. .A two -way valve 1 30 operated by means of solenoid 132 is included in the line for turning the air supply on and off at the proper time.

The heating assembly 'Iheheating assembly employed for heat-softening the plastic sheet clamped in the clamping frame is indicated at 140. It mounts a heating element 142 and is provided witha handle 144. 1 v

The hea'ter is, reciprocatablebetween a retracted position; wherein it is removed from the vacuum forming unit, and an advanced position, wherein it; is stationed opposite the clamping frame unit thereof forsoftening the plastic, To this end. a plurality of flanged wheels 146 are rotatably mounted on the sides of the heater. These rides in tracks 148. p v Tracks148 may comprise a pair of ,opposedvchann'el irons mounted on brackcts lsd extendingupwardly from housing 12 of the unit so that the heater may be advanced against the forcevof gravity and then permittedto return to its retracted positiongravitationally. To maintain it In its advanced position for a desired period of tilninis provided with a finger l 5 2 which engages aiatchiisi when the heater is" advanced. Latch 154 is pivotally mounted on a pin 156 and may be released by the action of a solenoid 158. t V

The construction of latch 154 is illustrated in greater detail in Fig. 3. It is connected to rod 160 which in turn is connected to solenoid 158. A compression spring 162 encircles the rod and bears against a perforated plate 164, in which the rod slides, and against a washer 166, which is rigid to the rod. Hence as the heater is advanced, finger 152 engages latch 154. However, after an appropriate .time interval, the latch may be opened by operation of solenoid 158 against the force of spring 162. Then after the solenoid is de-energized, the spring returns the latch toits advanced position.

The electric control circuit The electric control circuit by means of which, the various units described above may be operated is illustrated in Fig. 1. The circuit is connected to the house line through master switch 170. Closing this switch energizes a transformer 172 which in turn energizes an automatic timingunit .174. Suitable circuits'are included for manual and automatic operation. Theseare selected by means'of manual-automatic switch 176 and include a manual frame lock, switch .178. The manual circuit includes a manual vacuum switch 180, a manual heater release switch 182, microswitches 186, 188' which are operated by opening and closing of the clamping frame assembly and a switch 190 operated by solenoid 192.

The circuit for automatic operation includes the foregoing switches with. the exception of manual switches 180,182. It includes also switch 194 operated by solenoid 196, and a microswitch 197 which is opened and closed by the action of finger 152.

General operating cycle The basic operating sequence of the herein described packaging apparatus is as follows: 7

Articles 10 to be packaged are placed on vacuum chamber, 30., They may be placed directly on perforated plate 32 or, if it is desired to include a backing sheet in the package assembly, they may be placed on a porous, fibrous sheet 198 having thereover a perforated layer 200 of thermosensitive adhesiveKFig. 7). Backing sheet 198 may comprise, for example, a shectiof ordinary cardboard of suitable thickness, the inherent porosity of the cardboard being adequate for the present purposes.

If articles are to be produced or packaged which require a female mold, mold box extension 84 may be inserted between plate 32 and lower clamping frame member 40. z

1 Next, the opening between the clamping frame members .40, 42'may be adjusted to suit the thickness of the plastic byadjustrnent of bolts 80. Plastic sheet 18 then is clampedbetween the frame members and heater 140, which is maintained continuously energized, advanced until it lies above the clamping unit. After the plastic has been softened, the clamping unit is retracted, draping the's'oftened material over the articles.

Vacuum box 30 then may be evacuated, forming the plastic about the articles. Heating may be continued as long as desired to activate thermosensitive plastic 200 on the porous backing sheet, if such is employed. The heater then, is retracted. After the plastic is cool, the vacuum supply may be disconnected from vacuum box 30, atmospheric air or air under pressure admitted thereto for cleanly separating the plastic sheet with its enveloped'packaged articles from plate 32 and the clamping frame elevated. The plastic sheet then may be cut off at the infeed side and the clamping frame opened to complete the packaging cycle.

Manual operation In the usual plant operation it is highly desirable to haveavailable plastic packaging apparatus which may be operated manually as well as automatically. Manual operation is. desirable, for example, during the experimental period which maybe required for working out the vacuum and time sequences to be used for packaging articles of a particular class with a thermoplastic sheet of designated thickness and properties. Also, it may be desirable where only a few items of a given class are to be packaged and it is desired to avoid adjustment of a pre-set automatic timing cycle.

The manual operation of the apparatus may be varied as required for drape-vacuum forming, drape forming only, or vacuum forming only. In all three of these situations the clamping frame opening is adjusted, vacuum valve 114 is set by adjusting switch 118, the master switch is closed, automatic-manual switch 176 'is set on manua and the articles are loaded on the platen.

Closing master switch 170 energizes heater 142; motor 122, which drives the vacuum pump and solenoid 116 and switch 118 which determine the setting of vacuum valve '114, which, in turn, determines the vacuum in tank 34 communicating with'the vacuum chamber 30, full vacuum being always applied to tank 110 which communicates with vacuum cylinders 90, 92, driving the reciprocatingclamping frame. Closing the master switch also energizes timer 174 through which the various ciredits of the unit are energized.

With the master switch closed, the heater energized, the articles loaded on perforated plate 32, and plastic sheet 18 clamped in the clamping frame, the heater is advanced up inclined tracks 148 until it registers with the clamping frame. It is latched in this position by solenoid-operated latch 154. Microswitch 197, however, is inoperative because of the manual setting of switch 176.

After the plastic has become soft, as determined by visual observation or by the lapse of a predetermined time interval, manual vacuum'switch 180 is closed. This has several consequences.

First,.it energizes solenoid 196, closing contacts 194, energizing solenoid 102. This'solenoid adjusts four-way valve 100 to a setting in which vacuum is applied to line 96 through throttle valve 106. As a result, the cylinders are retracted at a predetermined speed, drawing the clamping frame and softened plastic downwardly and draping the plastic overthe articles.

Microswitches 186, 188 are closed by the frame as it seats to form an air tight inclosure around the articles. Microswitch 186 energizes solenoid 38, operating valve 36 so as to admit vacuum to the chamber 30 of an intensity determined by the setting of pressure switch 118. The vacuum thus tucks the plastic around the articles, and sucks it into firm engagement with thcrmosensitive adhesive 200 on backing sheet 198, if a backing sheet has been employed.

A secondary result of closing manual vacuum switch 180 is to energize solenoid 192, which operates to open contacts 190 inthe circuit of solenoid 132. Thus when microswitch188 is closed by the action of lowering the frame, it is rendered inoperative.

At this point, manualheater release switch 182 may be closed. This switch, being in series with solenoid 158, releases latch 154 so that heater can gravitate downwardly to its rest position, removed from the packaging location.

After the plastic has cooled, manual vacuum switch is opened. This instantly de-energizes solenoid 192 so that contacts are closed, completing the circuit through solenoid 132 since microswitch 188 is still held closed by the lowered clamping frame. Solenoid 132 operates valve 130 so that air at atmospheric or superatmospheric pressure is admitted to the vacuum chamber.

At the same time, solenoid 196 is deenergized, allowing contacts 194 to open, which de-energizes solenoid 102. The four-way valve 100 is thereby returned to its original position wherein conduits 98 and 94 are connected to vacuum tank 110. As a result, piston rods 90 of cylinders 92 are advanced and the clamping frame 9 of adhesive may be used on the backing sheet, if employed, with no decrease in adhesive qualities.

The apparatus is readily adaptable to experimental use. The operator is protected while loading. The plastic roll may be used either from the right or left side to suit the layout of a given production line.

In addition, the vacuum applied is adjustable to accommodate fragile articles which will not stand full atmospheric pressure. The rate of frame pull down is controllable so as not to force the parts out of position during the downstroke of the clamping frame, the stretch of heavy plastic also being controlled.

Still further, the products are clearly visible at all times. Drape or vacuum forming techniques may be employed. A minimum amount of costly plastic need be trimmed ofi. Finally, the machine is of simple, inexpensive construction and may be easily disassembled for effective servicing.

It is to be understood that the form of my invention herein shown and described is to be taken as a preferred example of the same and that various changes in the shape, size and arrangement ofparts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In apparatus for packaging articles in a thermoplastic sheet, wherein the apparatus includes a perforated support for articles to be packaged, a sheet supporting frame disposed adjacent the article support and movable toward and away from the latter, heating means disposed adjacent the frame on the side thereof remote from the article support and adapted to heat and soften a thermoplastic sheet supported in the frame, and vacuum means communicating with the perforations in the article support for wrapping a softened sheet about an article: the combination therewith of vacuum control valve means 'for controlling vacuum to the article support, and actuating means for the vacuum control valve means and operable by the frame upon movement of the latter toward the article support to open the vacuum means to the article support and wrap the sheet about the article.

2. The combination of claim 1 wherein the actuating means for the vacuum control valve means comprises electrical actuating means having an electric circuit, and switch means in the electric circuit operable by the frame.

3. In apparatus for packaging articles in a thermoplastic sheet, wherein the apparatus includes a perforated support for articles to be packaged, a sheet supporting frame disposed adjacent the article support, heating means disposed adjacent the frame on the side thereof removed from the article support and adapted to heat and soften a thermoplastic sheet supported in the frame, and vacuum means communicating with the perforations in the article support for wrapping a softened sheet about an article: the combination therewith of air pressure means communicating with the perforations in the article support for stripping the sheet and wrapped article from the article support, air pressure control valve means for controlling air pressure to the article support, and actuating means for the air control valve means and operable upon completion of the wrapping of the article to introduce air pressure to the article support and strip the sheet therefrom.

4. The combination of claim 3 wherein the actuating means for the air pressure control valve means comprises electrical actuating means having an electric circuit, and switch means in the electric circuit operable upon completion of the wrapping of the article.

5. In apparatus for packaging articles in a thermoplastic sheet, wherein the apparatus includes a perforated support for articles to be packaged, a sheet supporting frame disposed adjacent the article support and movable toward and away from the latter, heating means disposed adjacent the frame on the side thereof remote from the article support and adapted to heat and soften a thermoplastic sheet supported in the frame, and vacuum means communicating with the perforations in the article support for wrapping a softened sheet about an article: the combination therewith of vacuum control valve means for controlling vacuum to the article support, actuating means for the vacuum control valve means and operable by the frame upon movement of the latter toward the article support to open the vacuum means to the article support and wrap the sheet about the article, air pressure means communicating with the perforations in the article support for stripping the sheet and wrapped article from the article support, air pressure control valve means for controlling air pressure to the article support, and actuating means for the air control valve means and operable upon completion of the wrapping of the article to introduce air pressure to the article support and strip the sheet therefrom.

6. The combination of claim 5 wherein the actuating means for the vacuum control valve means comprises electrical actuating means having an electric circuit, and switch means in the electric circuit operable by the frame, and wherein the air pressure control valve means comprises electrical actuating means having an electric circuit, and switch means in the electric circuit operable upon completion of the wrapping of the article.

7. In apparatus for packaging articles in a thermoplastic sheet, wherein the apparatus includes a perforated support for articles to be packaged, a sheet supporting frame disposed adjacent the article support, heating means disposed adjacent the frame on the side thereof remote from the article support and adapted to heat and soften a thermoplastic sheet supported in the frame, and vacuum means communicating with the perforations in the article support for wrapping a softened sheet about an article: the combination therewith of inclined support means for the heating means and arranged for retracting the heating means by gravity from its position adjacent the sheet supporting frame, latch means releasably securing the heating means against retraction, and actuating means for the latch means and operable to release the latter to effect retraction of the heating means.

8. The combination of claim 7 wherein the actuating means for the latch means comprises electrical actuating means having an electric circuit, and switch means in the electric circuit operable to release the latch and effect retraction of the heating means.

9. In apparatus for packaging articles in a thermoplastic sheet, wherein the apparatus includes a perforated support for articles to be packaged, a sheet supporting frame disposed adjacent the article support and movable toward and away from the latter, heating means disposed adjacent the frame on the side thereof remote from the article support and adapted to heat and soften a thermoplastic sheet supported in the frame, and vacuum means communicating with the perforations in the article support for wrapping a softened sheet about an article: the combination therewith of vacuum control valve means for controlling vacuum to the article support, actuating means for the vacuum control valve means and operable by the frame upon movement of the latter toward the article support to open the vacuum means to the article support and wrap the sheet about the article, air pressure means communicating with the perforations in the article support for stripping the sheet and wrapped material from the article support, air pressure control valve means for controlling air pressure to the article support, actuating means for the air control valve means and operable upon completion of the wrapping of the article to intro duce air pressure to the article support and strip the sheet therefrom, inclined support means for the heating means and arranged for retracting the heating means by gravity from its position adjacent the sheet supporting frame, latch means releasably securing the heat means against retraction, and actuating means for the latch M1 means and operableto release thelatter' to elfect'retraction of-the heating. means.,r. rt i a 710. The combination of claim 9 whereintheactuating means, for vthe vacuum control ,valve means comprises electrical actuating means having an ,electric circuit, and switch means in the electriccircuit operable by the frame, and wherein the actuating meausforthe air pressure controhvalve means comprises electrical ,actuating means having an electric circuit, vandswitch means in the electric circuit operable upon completionhof the .wrapping of the article, and, e nthe actuating ,meansfo-r, the. latch means comprises electrical .actuating means. having an electric circuit,v andiswitchmeans in,, the electric circuit operableto. release the latch and efiect retraction of the heating means. a r .11. The combination of claim 9, including reciprocative fluid, pressure Qperatingmeans. supporting, -.the frame for moving the latter toward and away from the article support, fluid pressure control valve .1 means for, controlling fluidtpressuretorthe operating means,and actuating means for the fluid pressure means operable to control the reciprocation of the fluid pressure operating means.

References Qitliil in thetile of this patent UNITED STATES PATENTS 1,856,694 DZ; cerrwm y 3, 1932 1,980,022 Whiteh0use Nov. 6, 1934 2,690,593 Aberc rom'bie Qct. 5, 19 54 2,750,719 Wandelt June 19, 1956 I FOREIGN PATENTS I 201,271 Australia Mar. 19, 1956 

